Method of etching glass

ABSTRACT

A method of etching glass, and particularly relatively large glass plates, to provide art form panels. A material resistant to acid, such as asphaltum, is applied to a surface of the glass plate with the exposed portion of the surface constituting the pattern to be etched. The backside and edges of the plate are masked with a coating of an elastomer covered with an acid resistant material, such as asphaltum. The panel is placed in a bath of hydrofluoric acid having a concentration of 20 percent to 30 percent with the surface to be etched facing downwardly. During the etching process the bath is maintained at a temperature of about 80*F and the panel is maintained in the bath for the desired period of time to obtain a deeply etched pattern. After etching the panel is removed, neutralized and rinsed with water.

waited States Eatent Gruenke, J r.

[111 3,769,113 1 Oct. 30, 1973 METHOD OF ETCHING GLASS [75] Inventor:Bernard E. Gruenke, Jr.,

Menomonee Falls, Wis.

[73] Assignee: Conrad Schmitt Studios, Inc.,

Milwaukee, Wis.

[22] Filed: Apr. 1, 1971 [21] Appl. No.: 130,309

[52] 11.8. C1. 156/24, 65/31 [51] Int. Cl. C03c 15/00 [58] Field ofSearch 156/13, 8, 24, 14, 156/345; 65/31 [56] References Cited UNITEDSTATES PATENTS 2,529,703 11/1950 Nicoll et al. 156/24 243,200 6/1881Bradley 156/13 95,617 10/1969 Strauss 156/13 135,039 1/1973 Johnston...156/13 3,390,060 6/1968 Badi 156/13 X 1,974,011 9/1934 Burgess 156/13Primary Examiner-.l. Steinberg Att0rneyAndrus, Sceales, Starke & Sawall[57] ABSTRACT A method of etching glass, and particularly relativelylarge glass plates, to provide art form panels. A material resistant toacid, such as asphaltum, is applied to a surface of the glass plate withthe exposed portion of the surface constituting the pattern to beetched. The backside and edges of the plate are masked with a coating ofan elastomer covered with an acid resistant material, such as asphaltum.The panel is placed in a bath of hydrofluoric acid having aconcentration of 20 percent to 30 percent with the surface to be etchedfacing downwardly. During the etching process the bath is maintained ata temperature of about 80F and the panel is maintained in the bath forthe desired period of time to obtain a deeply etched pattern. Afteretching the panel is removed, neutralized and rinsed with water.

8 Claims, 3 Drawing Figures PAIENIEBBBI 30 ms FIG. 2 5 k INVENTOR.BERNARD E. GRUENKE. Jr?

ATTORNEYS METHOD or ETCHING GLASS BACKGROUND OF THE INVENTION Glassarticles have normally been etched in the past by masking certainportions of the glass article with acid resistant material, such asasphaltum, and then subjecting the exposed surfaces to hydrofluoric acidwhich will attack and etch the exposed glass.

In the traditional methods hydrofluoric acid is applied to the glassarticle by pouring or brushing the acid on the surface to be etched, orin some cases, the article is placed in an acid bath. In the techniquesused in the past, the article was normally subjected to the action ofthe acid for a period of only several minutes to provide a generallymatte finish for the exposed portions of the glass.

SUMMARY OF THE INVENTION This invention relates to a method of etchingglass and partocularly to etching relatively large glass plates for useas art form panels. In accordance with the process of the invention, amaterial which is resistant to acid, such as asphaltum, is applied to asurface of the glass plate in a desired pattern with the exposedportions of the glass surface constituting the design to be etched. Thebackside of the plate is coated with an emulsion of an elastomer, suchas latex or acrylic resin, and after drying, a layer of asphaltum isapplied to the dried coating of the elastomer. The edges of the platecan be masked either by acid resistant tape, or applying coatings of theelastomer and asphaltum to the edges.

After proper masking, the plate is placed in a bath of hydrofluoric acidwith the surface to be etched facing downwardly. The acid preferably hasa strength in the range of 20 percent to,30 percent and is maintained ata temperature of about 80F. To provide the desired deeply etchedpattern, the plate is maintained in the bath for a period of 17 to 24hours and after this period, the plate is removed from the bath,neutralized and rinsed with water. The masking is then removed from theplate.

The process of the invention provides a deeply etched pattern, which hasunusual edge contours providing a very striking appearance for thepanel. The downward disposition of the surface to be etched in the acidbath is particularly important in providing this unusual etched contour.

The plates etched in accordance with the process of the invention can beused for windows, dividers, or decorative panels in churches, officebuildings, schools, hospitals, theatres, or the like. While theinvention has particular application to the etching of glass plates, itcan also be used to etch mirrors or other glass articles.

Other objects and advantages will appear in the course of the followingdescription.

The drawings illustrate the best mode presently contemplated of carryingout the invention.

In the drawings:

FIG. 1 is a perspective view of a glass panel etched in accordance withthe process of the invention;

FIG. 2 is a cross section of the glass panel showing the etchedcontours; and

FIG. 3 is a fragmentary vertical section showing the glass plate locatedwithin the acid bath.

FIG. 1 illustrates a glass plate 1, which is etched in accordance withthe process of the invention. The etched pattern in the glass can be anydesired design or configuration, and may take the form of figures,landscapes, abstract designs, or the like.

In accordance with the process of the invention, a coating 2 of an acidresistant material, such as asphaltum, wax or the like, is initiallyapplied to one surface 3 of the glass plate 1 in the form of a patternor design. The exposed portion of the glass surface constitutes thepattern to be subsequently etched. If a specific design or figure is tobe applied to the surface of the plate, a convenient method of applyingthe same is to position a drawing of the design beneath the transparentglass plate. The drawing can then be traced on the upper surface of theplate using the asphaltum or wax. On the other hand, if an abstractdesign is to be applied to the surface of the plate, the asphaltum canbe applied directly to the surface of the plate in the desired pattern.

Various surface textures can be achieved in the final etched product byvarying the manner in which the acid resistant material is applied tothe plate surface. For example, if the acid resistant material isapplied to certain areas of the plate as a continuous dense coating,etching of these masked areas will be prevented. A stippled pattern ofetching can be achieved by applying the acid resistant material with asponge or foam rubber. In addition, the material can be applied to thesurface by use of strings, squeeges, rollers, crinkled paper, or anyother manner to provide an interesting abstract design.

The backside 4 of the glass plate is preferably protected during theetching process by applying a suspension of an elastomer 5, such as arubber latex or acrylic resin, to the backsurface of the plate. Afterdrying, an outer protective coating of asphaltum of wax 6 can be appliedover the elastomeric layer. The use of the clastomer on the backside hasan advantage in that after the etching process has been concluded, theelastomeric coatingcan be stripped from the glass surface in the formofa single sheet, as opposed to the asphaltum, which must be scrapedfrom the glass surface.

The edges 7 of the glass plate can be protected by either using an acidresistant tape which is applied to the edge surfaces, or alternately, byapplying coatings of the elastomer and asphaltum to the edges in amanner similar to that described with respect to the back surface. 7

After the desired design has been applied to the surface 3 of the plate,and the edges 7 and back surface 4 have been satisfactorily masked, theplate is placed in avat or tank 8 containing hydrofluoric acid 9, asillustrated in FIG. 3. The construction of the vat 8 itself forms nopart of the invention, and the inner surface of the vat is preferablylined with lead or other material which will resist the corrosive.attack of the hydrofluoric acid. As shown in FIG. 3, the plate 1 issubmerged within the hydrofluoric acid bath 9 and the surface to beetched faces downwardly toward the bottom of the vat and is spaced fromthe bottom surface by a series of supports 10. While FIG. 3 shows asingle glass plate 1 located in the vat, in practice, racks containing aseries of plates can be positioned in the vat.

While the thickness of the glass plate 1 is not critical to theinvention, it has been found that a deeply etched pattern is moststriking, and therefore, the glass preferably has a thickness in therange of three-eighths to one-half inches and it is preferred that theetched areas have a depth up to one-fourth inches.

The acid preferably has a concentration in the range of 20 to 30 percentby weight, and during the etching process higher concentration acid canbe added to the bath, if necessary, to maintain the concentration in thedesired range.

Most favorable etching results when the bath is maintained at atemperature in the range of 50F to 100F, and preferably about 80F.

As a deeply etched pattern is preferred, the plate is usually maintainedin the bath for a period of about 17 to 24 hours, with approximatelyhours being preferred.

In order to provide the desired etching pattern, the surface 3 to beetched should face downwardly in the bath. This downward disposition ofthe surface to be etched has advantages in that it results in theformation of tapered or sloped areas connecting the unetched and fullyetched regions. As shown in FIG. 2, the portion of the surface 3 coveredby the asphaltum 2 will not be attacked by the acid. As the surface tobe etched faces downwardly, the exposed glass is etched away in asloping pattern as indicated by the areas 11. This etching action isdifferent from that which occurs if the surface to be etched facesupwardly, in which case the acid would attack and undercut the areabeneath the protected portions 2, so that the sloping areas 11 would notbe present. Facing the surface to be etched downwardly has the addedadvantage that any glass particles which are dislodged by the corrosiveattack of the acid will fall downwardly by gravity and will be removedfrom the surface to be etched.

After the etching operation has been concluded, the glass plate 1 isremoved from the acid bath and preferably neutralized with lime or otheralkaline material and then rinsed with water. After rinsing, the plateis cleaned of all the asphaltum and the elastomer, rinsed again, dried,and is then ready for installation. As previously noted, the layer ofthe elastomer enables the entire protective film on the backsurface ofthe plate to be readily stripped therefrom, while the asphaltum on theopposite surface must be scraped away.

The glass panels produced by the method of the invention have a deeplyetched pattern with unusual striated contours interconnecting the fullyetched and unetched portions of the surface. Any desired pattern ordesign can be etched in the glass surface such as portraits, figures,landscapes, abstract designs, and the like.

The panels produced by the process of the invention can be used aswindows, decorative panels, or dividers, in churches, office buildings,schools, hospitals, theatres, or the like. While the process hasparticular application to the etching of large glass plates, it can alsobe used for smaller glass objects.

Various modes of carrying out the invention are contemplated as beingwithin the scope of the following claims particularly pointing out anddistinctly claiming the subject matter which is regarded as theinvention.

I claim:

1. A method of etching glass, comprising the steps of applying a patternto a surface of a glass article with an acid resistant material, withthe remaining exposed portion of the glass surface constituting the areato be etched, positioning the glass article in a bath of an acid capableof attacking the glass with the exposed portion of the glass articlefacing downwardly within the bath, maintaining the temperature of thebath in the range of 50F to lO0F, said acid acting to attack and etchthe exposed portion of the glass to provide the desired etched pattern,and removing the article from the bath.

2. The method of claim 1, wherein the bath is an aqueous solution ofhydrofluoric acid having a concentration in the range of 20 percent to30 percent by weight.

3. The method of claim 1, and including the step of maintaining theglass article in the bath for a period of 17 to 24 hours.

4. The method of claim 1, wherein said glass article is a glass platehaving a front surface to be etched and having a back surface and havingedges connecting the front and back surfaces, said acid resistantmaterial being applied to the edges and the back surface to completelycover the same.

5. A method of etching a surface of a glass plate having a firstsurface, an opposed second surface and edges connecting said first andsecond surfaces, comprising the steps of applying a pattern to the firstsurface of the glass plate with an acid resistant material, theremaining exposed portion of said first surface constituting the area tobe etched, applying an acid resistant material to the edges of theplate, applying a coating of an elastomer to the second surface of theplate, applying a coating of an acid resistant material over saidelastomer on said second surface, positioning the plate generallyhorizontally in an aqueous bath of hydrofluoric acid having aconcentration in the range of 20 percent to 30 percent by weight andfacing said first surface downwardly within said bath, maintaining saidplate in said bath for a period of 17 to 24 hours to cause said acid toattack and etch the exposed portions of the first surface, and removingthe plate from the bath.

6. The method of claim 5, wherein said bath is maintained at atemperature of about 50F to F.

7. The method of claim 5, wherein said acid resistant material appliedto the edges of the plate comprises an acid resistant tape. 7

8. The method of claim 5, wherein said acid resistant material isasphaltum.

2. The method of claim 1, wherein the bath is an aqueous solution ofhydrofluoric acid having a concentration in the rAnge of 20 percent to30 percent by weight.
 3. The method of claim 1, and including the stepof maintaining the glass article in the bath for a period of 17 to 24hours.
 4. The method of claim 1, wherein said glass article is a glassplate having a front surface to be etched and having a back surface andhaving edges connecting the front and back surfaces, said acid resistantmaterial being applied to the edges and the back surface to completelycover the same.
 5. A method of etching a surface of a glass plate havinga first surface, an opposed second surface and edges connecting saidfirst and second surfaces, comprising the steps of applying a pattern tothe first surface of the glass plate with an acid resistant material,the remaining exposed portion of said first surface constituting thearea to be etched, applying an acid resistant material to the edges ofthe plate, applying a coating of an elastomer to the second surface ofthe plate, applying a coating of an acid resistant material over saidelastomer on said second surface, positioning the plate generallyhorizontally in an aqueous bath of hydrofluoric acid having aconcentration in the range of 20 percent to 30 percent by weight andfacing said first surface downwardly within said bath, maintaining saidplate in said bath for a period of 17 to 24 hours to cause said acid toattack and etch the exposed portions of the first surface, and removingthe plate from the bath.
 6. The method of claim 5, wherein said bath ismaintained at a temperature of about 50*F to 100*F.
 7. The method ofclaim 5, wherein said acid resistant material applied to the edges ofthe plate comprises an acid resistant tape.
 8. The method of claim 5,wherein said acid resistant material is asphaltum.